Seal assemblies or packers are frequently used in the oil and gas industry for sealing an annulus in a wellbore, such as may exist between a bore wall and a mandrel. Such sealing may be achieved by use of annular components which are mounted on a mandrel and which extend between the mandrel and bore wall. Such annular sealing components may include annular sealing bands, cup seals, inflatable bladders, swellable elements and the like.
It is often required to provide a seal which is capable of being run into a wellbore while defining a minimal outer diameter, for example to pass through wellbore restrictions, and then be radially expanded to provide a seal against a bore wall. However, high expansion ratios are often difficult to achieve, and it is well known in the art that excessive expansion ratios are often only achievable at the expense of performance. For example, a highly expanded seal may perform poorly against high pressures and may be susceptible to axial leakage and extrusion.